Degree

Doctor of Philosophy (PhD)

Department

Physics and Astronomy

Document Type

Dissertation

Abstract

The 17F(α, p)20Ne reaction has been identified as an alternate pathway for breakout from the hot-CNO cycle that can be important in some X-ray burst scenarios. The 17F(α, p)20Ne reaction rate was previously determined through a parameterized exponential S-factor with a large enhancement from thermally-excited states based on statistical models with large uncertainties. We have measured the time-inverse 20Ne(p,α)17F cross section at center-of-mass energies ranging from 5.50 to 7.10 MeV using an activation method with a proton beam on a neon gas cell. Coincident detections of 511-keV γ-rays, resulting from electron-positron annihilation following the decay of of 17F, were made using NaI detectors at the John D. Fox Superconducting Accelerator Laboratory at Florida State University. We also measured the same reaction through inverse kinematics with a 20Ne beam on a polypropylene target at the Argonne Tandem Linac Accelerator System facility at Argonne National Laboratory using an annular Si strip detector for alpha detection with recoiling heavy ions detected in coincidence in the Enge split-pole spectrograph by the MONICA focal plane detector. Studying the inverse kinematics reaction allowed us to distinguish alpha particles being emitted either to the ground or first-excited states of 17F. Cross sections have been analyzed along with data from previous works using an R-matrix formalism to constrain the properties of states in 21Na. This results in the first determination of the 17F(α, p)20Ne reaction rate based on individual nuclear level proper- ties. Uncertainties in reaction rates were determined by varying resonance properties in energy regimes where we do not have data to serve as a constraint.

Date

11-3-2025

Committee Chair

Blackmon, Jeffery C.

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